0
refer the article http://www.msha.gov/S&HINFO/TECHRPT/GROUND/SAFEMEAS.pdf
Wiki User
∙ 16y ago
Wiki User
∙ 11y agofor electrical system in building it will be not more thane 5 ohm for lightening protection it not more thane 0.5 ohm
Add your answer:
Earn +20 pts
What is resistance expressed in?
Electrical resistance is measured in Ohms.
What does the two terminal test method measure?
Measures the resistance to earth from a grounding system
What is excessive electrical resistance?
High resistance means insulation
How do you earth in the 1600 kva transformer?
In 1600 kva transformer we provide NGR (Neutral grounding resistance)
Is high electrical resistance good or bad?
electrical resistance is when something resists the electrical current .. eg rubber hope it helped
Classification, basic concepts and installation of grounding devices?
Grounding device is also called grounding integration device: a device that forms an electrical connection between electrical equipment or other objects and the ground. (Building Electrical Construction Technology). The grounding device consists of a grounding electrode (plate), a grounding busbar (indoor and outdoor), a grounding down-conductor (grounding jumper), and a frame grounding. It is used to realize the purpose of connecting the electrical system to the earth. The metal object that is in direct contact with the ground for electrical connection is the ground electrode. It can be an artificial ground electrode or a natural ground electrode. This grounding electrode can be assigned some electrical function, such as being used as system grounding, protective grounding or signal grounding. The grounding busbar is the reference potential point of the electrical installation of the building, through which the part that needs to be grounded in the electrical installation is connected to the grounding electrode. It also serves another function, that is, by interconnecting the equipotential bonding lines in the electrical installation, the overall equipotential bonding between the large conductive parts of a building is realized. The connection line between the grounding electrode and the grounding busbar is called the grounding electrode lead. Safety isolating transformer safety isolating transformer. Transformers that supply tools, other equipment and distribution circuits with safe extra-low voltage. Its input winding and output winding are electrically isolated by at least the equivalent of double insulation or reinforced insulation. Next, an excellent grounding device manufacturer, Sichuan Sunlight intelligent electric equipment Co., Ltd, will introduce the classification of grounding devices, basic concept of grounding device resistance and installation of grounding device. Classification of grounding devices The grounding device is composed of a grounding body (round steel, angle steel, flat steel, steel pipe, etc.) buried in the soil and a grounding wire for connection. According to the purpose of grounding, the grounding of electrical equipment can be divided into: working grounding, lightning protection grounding, protective grounding, and instrument control grounding. Working grounding: It is the grounding required to ensure the normal operation of the power system. For example, the neutral point of the transformer in the neutral point direct grounding system is grounded, and its function is to stabilize the potential of the power grid to the ground, thereby reducing the insulation to the ground. Lightning protection grounding: It is the grounding set for the needs of lightning protection. For example, the grounding of lightning rods (wires) (now called lightning rods, wires, strips) and arresters is to make the lightning current smoothly lead to the ground, so as to reduce the lightning overvoltage, so it is also called overvoltage protection grounding. Protection grounding device: also known as a safety grounding device, it is a grounding device set up for personal safety, that is, the electrical equipment shell (including the cable sheath) must be grounded to prevent the shell from being charged and endangering personal safety. Instrument control grounding device: the thermal control system, data acquisition system, computer monitoring system, transistor or microcomputer type relay protection system, and telecontrol communication system of the power plant, etc., are set up to stabilize the potential and prevent interference. Also known as an electronic system grounding device. The above is the classification of grounding devices. basic concept of grounding device resistance The resistance of the grounding device refers to the resistance encountered when the current passes through the grounding body into the earth and spreads around. The earth has a certain resistivity, and if there is current flowing through it, the earth has different potentials everywhere. After the current is injected into the ground through the grounding body, it spreads around in the form of a current field. 15~20m away), the resistance per unit diffusion distance and the current density in the ground are close to zero, and the potential here is zero. The curve U=f(r) in the figure represents the potential distribution on the ground surface (r represents the distance from the lightning current injection point). The above is the basic concept of grounding device resistance. Installation of grounding device
How important is the ground wire for a chandelier?
The grounding of all electrical equipment is very important. So much so that it is an electrical code rule required in any electrical installation.
Why neutral of generator is resistance grounded and neutral of motor is reactance grounded?
You can use resistance or reactance grounding on generators and motors. My understanding is resistance grounding is often used to limit ground fault currents to a few amperes, while reactance grounding will limit fault current to less than the three phase fault current. If reactance grounding is used to limit fault current o very little (like resistance grounding), transient overvoltage problems can occur.
What section of the nec covers grounding?
Article 250 of the National Electrical Code covers grounding.
Do you have to have a safe and efficient grounding system?
It is an electrical code requirement that every service must have a grounding system.
How do you check with mega that you have good grounding on electrical circuit?
when you say "mega" I am asuming you mean meggar-ohmmeternot the lottery This instrument is not appropriate to test for good grounding Good grounding requires LOW resistanceA Meggar is used for measuring for HIGH resistances You need a MICRO-ohmmeter or ground resistance meter A company called AEMC makes nice ground testers
Why do synchronous motors have reactance grounding but synch alternators have resistance grounding?
remember the power flow equation Pm-Pe = Pa(accelerating Power) = 2H/Ws ddelta/dt 1. synchronous generator resistance grounding - when system suffer any kind of the disturbance which results in Pa accelerating power increases due to increase in Pe electrical power.to keep the balance between Pe and Pm, we reduce the increase amount of Pe electrical power by dissipated in the resister. from above equation we can easily make understand the Pm= Pe (in stability condition) 2. synchronous motor inductance grounding - Reverse explanation in case of motor
How do lighting rods proctect structures?
By grounding electrical energy.
What is the acceptable value of grounding resistance for any application?
An acceptable resistance for a ground to ground plate system is 2 ohms with a maximum allowance to 5 ohms. If the measured resistance is above 5 ohms more grounding rods or plates have to be added to reduce the resistance down to the acceptable levels.
What measures electrical resistance?
an ohm meter OR multimeter is used to measure the electrical resistance...
What is the opposition to the flow of electrons is called?
Resistance, or electrical resistanceResistance, or electrical resistanceResistance, or electrical resistanceResistance, or electrical resistance
What is international standard for electrical grounding?
Less than 1 Ohm.
